Thermoplastic self-supporting thin film of the kind which clings strongly to itself and other surfaces has been rolled in various lengths and sold in dispensing cartons to the public mainly for household use. Although this type of household product has found wide acceptance, one complaint has been the difficulty in locating and separating the leading edge of the cling film to initiate the start of the roll. Once the leading edge of the film is separated from the underlying layer of film, a desired length of film is peeled from the roll and severed using any of the conventional cutting means employed on the customary carton in which the roll is packed. The leading edge of the film remaining after the severing and removal of the desired length of film is usually pressed against the wall of the carton so as to be ready when an additional length of film is required. Consequently, it is the initial leading edge of a new roll of packed cling film that is difficult to locate or find and difficult to peel away to start the roll. Although film roll starting means or convenience features have been employed with some success to initiate the start of a roll, the difficulty in providing such means or features from a manufacturing standpoint has sometimes created problems for the manufacturer.
One proposed solution to solve the problem whereby the leading edge of a cling film adhere to the underlying layer of film is disclosed in U.S. Pat. No. 3,945,495. Specifically, this patent discloses the concept whereby the leading edge of the roll is treated or coated with a substance that unbalances the degree of shrinkage at the opposite surfaces of the edge such that the edge will curl, preferably away from the surface of the roll, during storage. An apparent limitation or drawback in this approach is that a coating step has to be performed on the film prior to it being packaged in a consumer type dispensing carton.
Another proposed solution is to emboss the leading edge of the roll using a conventional heat platen or strip to reduce the blocking or sticking of the edge of the film to the underlying layer. This approach, as generally discussed in U.S. Pat. No. 3,501,363, entails the feeding of the film between a heated steel roll, or platen secured to a roll, having a desired pattern etched or cut into its surface and a firm rubber-type backup roll so that by using conventional actuator means, such as a hydraulic ram, one of the rolls can be urged against the other roll thereby causing the segment of film therebetween to be heated in selected areas. This selected heating of the film results in a corresponding shrinkage of small selected areas of the film thereby imparting to the surface of the film embossed raised and depressed areas. Embossing the film in this manner at high speeds, however, is difficult since the film generally intended for consumer use is relatively fragile and may be susceptible to breaking upon contact with the heated embossing platen or roll. Another drawback is the difficulty in maintaining the precise temperature control of the platen or roll since if either is too hot, it may excessively thin the film causing proneness to tear propagation and if either is too cold, the embossing may not be distinct enough to reduce blocking or sticking of the edge to the underlying layer.
In the normal production of cling film rolls in 50 feet (15.24 meters), 100 feet (30.48 meters), 125 feet (38.10 meters) or some other preselected length, the film is usually supplied from a supply source on a continuous basis to an embossing section of an apparatus where the heated etched platen is actuated to impart selective shrinkage areas to a transverse portion of the film. The film is then further fed to a rolling and severing station where it is continuously wound on a core into preselected length rolls and severed across the embossed segment of the film so that the embossed segment of the film will form the leading edge of the completed roll. As soon as one winding cycle approaches completion, the roll of film is automatically removed and an empty core is moved into position for receiving the leading edge of the remaining film being fed. Thus preselected lengths of rolled film are produced on a continuous basis. An apparatus for accomplishing this continuous operation is disclosed in U.S. Pat. No. 3,679,010 and is obtainable commercially from the Paper Converting Machine Company, Inc. as the 81" inches Poly Rewinder Machine 4769 . One drawback, however, is that during the operation of the apparatus, the embossed segment of the film sometimes is advanced or delayed out of proper coordination with the severing means resulting in the severing of the film at a location other than at the embossed segments. When this occurs, the apparatus is stopped and the timing for actuating the heat embossing platen has to be adjusted which usually takes about 20 minutes. In addition to this, the platens are expensive to resurface and more expensive to replace.
An object of the present invention is to provide an apparatus for continuously winding film into preselected length rolls with an embossing drum having on a transverse portion of its surface a removable projected nodulose segment which cooperates with an in-line support surface for imparting to selected transverse segments of a film strip being fed therebetween a substantially nodulose contour.
Another object of this invention is to provide a method for imparting a nodulose contour to selected transverse areas of a continuously fed film prior to the film being wound into rolls of various lengths.
Another object of this invention is to provide embossing means for use with film winding machines that is relatively inexpensive to make and requires a minimum of time to adjust.
Another object of this invention is to provide on a continuous and consistent basis rolls of cling film each having a leading edge that is readily identifiable and adapted for easy grasping to initiate the start of the roll.